The Bends

P

PoorBoy

New Member
Hello all. Working on my second build from all the inspirations on this site. This one is a typical Dyno/HF79 build. Only about 1/4 done now and I need some experienced input and wisdom. I have a AGK exhaust kit as a starting point but need to get more length and bends to have the muffler rearward of the pedals. Is there any suitable flex pipe that can be joined to the 1 inch tubing so the exhaust can easily snake rearward in a tight manner? My intent is to wrap the exhaust once completed as I like the look that it gives.

Perhaps my search terms were incorrect when using the Google search box. I am sure I can find a fabricator to bend something up however that expense money can be better used in another area of the build. Maybe not and that is why I seek you all out.
Note: engine is vertical mounted if that makes any difference and can post pictures if that also helps.

I do appreciate any and all input.

Tom
 
Map,

Thanks for the fast reply. That is what I felt would be available from someone. Since you use it, can you tell me if it lasts for a reasonable length of time? Or is that not even a consideration? Any pluses or minuses I should be aware of too?
Sorry to be a pest just trying get a good education.

Again, Thanks so very much.

Tom
 
PoorBoy said:
Map,

Thanks for the fast reply. That is what I felt would be available from someone. Since you use it, can you tell me if it lasts for a reasonable length of time? Or is that not even a consideration? Any pluses or minuses I should be aware of too?
Sorry to be a pest just trying get a good education.

Again, Thanks so very much.

Tom
Click to expand...

Most likely it will out last your bike unless you wash it down with salt water everyday, it is very durable stuff and easy to work with.

And you're very welcome sir.

Map
 
If you have a local Napa auto parts store you may also check with them, if they dont have it on hand they can most likely have you some in one day.

Map
 
Hey map thanks for that very intuitive video on U Tube about removing excess weight from the piston. Question... do those holes have to be perfectly measured from the others Because the only thing I'm prefect at doing exactly... is exactly nothing

The wedging of the piston is what I'm trying to do now with an old piston on a used parts build I'm doing it for a "top speed bike" I'm going to use 7000C street tires that are thin, thin, thin, shaving weight here and there I wanna hit 50 MPH for the first time !!

I will worry about slowing it down after I hit the 50 M.P.H. mark So right now brakes are an unnecessary weight I do not want !! :)
Again thanks for the info!!
 
Jumpa said:
Hey map thanks for that very intuitive video on U Tube about removing excess weight from the piston. Question... do those holes have to be perfectly measured from the others Because the only thing I'm prefect at doing exactly... is exactly nothing

The wedging of the piston is what I'm trying to do now with an old piston on a used parts build I'm doing it for a "top speed bike" I'm going to use 7000C street tires that are thin, thin, thin, shaving weight here and there I wanna hit 50 MPH for the first time !!

I will worry about slowing it down after I hit the 50 M.P.H. mark So right now brakes are an unnecessary weight I do not want !! :)
Again thanks for the info!!
Click to expand...

The holes don't have to be perfectly spaced between each other and as long as they're at least fairly close to the same I dont think it will create a problem, however.... it is very very important that the holes be drilled so that they are NEVER opened at all as they pass one of the ports whether it be intake, exhaust or the transfer ports, if they are it will create problems that will most likely cause terrible performance robbing issues and defeat the purpose of everything else that has been done.

Now I want to add some info here in regards to the holes being drilled in the piston I used in my engine.

The next one I do that way will only get 4 holes drilled in it most likely, one between each port and they will still be 3/16" in diameter, my reason for this is I'm not interested in going 50 MPH on one of my current bikes anymore, its just to dang fast on a regular bicycle and so I plan to build my bikes for low to mid 40's from now on, piston I have now that I drilled 12 holes in works great in the lower to lower mid rpm range and also works great in the extremely high rpm range, engine was very smooth running with very little vibes and very comfortable, BUT... yeah there is a big BUT to all of this also, and that is with the piston lightened as much as I did, the midrange 32 mph rpms got pretty rough so to cruise comfortably with that set up I need to keep the cruise speed below 32 MPH or run on up past that point to around 37+ MPH and then it will smooth back out from 37-38 MPH all the way to top speed in the higher RPMs and all the in between, it could be that this will not be the same with every Gen IV lower since the crank balance may not be exactly the same on each one, I don't think the slightly lighter piston actually added any extra top speed potential but it could have added a little possibly since the piston is easier to move being that it is lighter.

All I know is that I would rather have my engine deal with the mid range a bit smoother and not hit that growling rough spot in the low 30's since when I'm in town that is where I do most of my cruising and rarely cruise in the 40's in town accept for a couple of long stretches where the speed limit is 40 & 45 MPH.

Honestly I think notching the piston skirt on the intake side and changing port timing a bit by ramping piston @ exhaust and transfers is all that I will probably need to do to keep my bikes running at the cruise speeds I want and still have at least low to mid 40 MPH top speeds with all conditions being good.

Jumpa, I can tell you right now that 50 MPH on a regular bicycle is very fast and not easy to get done, you better have some good wheels, tubes, tires and brakes on that bike if it is gonna run those speeds, if not you could end up eating asphalt hard and fast....

I'm gonna try my drilled and cut piston in another Dax lower I have and see if that same rough spot exists at upper mid RPMs, if not then I'll know it was just the crank balance in that particular engine, but if it does it like the other lower I'll say that the piston was lightened to much for the mid range rpm's but is good for mid lows and upper highs rpms.

Be safe whatever you do Jumpa.....

Map
 
I am mocking up the exhaust using flex exhaust tubing. It will get welded to the stub on the exhaust flange near the engine and supported in 2 or 3 places as it exits the rear of the bike. It will be wrapped with exhaust wrap and coated too. Question though, is it too long and will performance suffer due to it's length?

Note: Front engine mount not installed yet and fenders not permanently removed.

Any comments on this exhaust or other are welcome as always.





 
On a four stroke, extra length will affect it very little as far as power output, and longer is quieter.
With four strokes, pipe size matters more than length usually, especially with a stock motor.
 
Looking Good there PoorBoy, makes me want to get a 4 Stroke build going... I have two GX200 Clones and two HF 79cc 4 strokes still new in the box, I have to many things going on right now to start something else but I think I may start a winter time project with one of them if all goes well.

looking forward to seeing this build of yours come together and to the finish.

Map
 
Thanks, Map

I would like to start a thread in the beach cruiser section.. Only o get criticism and evaluation as the build goes. I have spent weeks quietly reading threads and using the search function a lot. Hoping to get it done except for powdercoat in the next 4 weeks or sooner.

Tom
 
Got all my manifolds tig welded up as shown for the intake and exhaust. As you can see in the photo, I am using the stock exhaust manifold to the fabricated extension and then to an exhaust flex pipe with a muffler at the end near the rear axle. Welding shop tried to weld the flex to the pipe but were unsuccessful. Another welding shop perhaps? or is this too thin? So, any suggestions on mating the two? Clamp, braze, etc?

I do plan to wrap the pipe once all completed. Thanks guys.

Tom





 
Braze it, I have brazed the flex pipe to steel tubing with no problems.

The flex pipe is steel and not stainless steel right?

Map
 
I can see how the flex pipe would be hard to weld since its very thin layers of steel like it is, I've even torch welded it with an clothings hanger wire, but brsass is a little easier since the heat needed for brazing is less.

map
 
Nice setup... I agree on the brazing as well... that flex pipe just can't handle the quick heat trying to mig or arc weld it, I don't even thin I could tig weld that stuff either, but if you can get the header pipe hot enough to braze you should be able to without burning it up and you can use nickel/silver brazing rod if you want the braze to blend in with the silver colored pipe (just in case you decide not to wrap it it'll look nice), the nickel/ silver is also stronger than brass, but brass is plenty strong enough. I've brazed up exhaust pipes for my Buell using the Harley flange setup, a Jardine header, and a big twin Screamin Eagle muffler and it's held up just fine over the years.
 
Thanks, Davezilla.mi have some brazing rods coming soon and will Gide it a try. I will post once I give it a shot.
 
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